1. Field of Invention
The present invention relates to weapons, more particularly to cartridge bores for weapons adapted to fire different calibers.
2. Description of Prior Art
U.S. Pat. Nos. 4,543,741 and 5,341,587 of which Applicant is inventor, provided ejector and cartridge positioner mechanisms which permit weapons to fire any of several different caliber cartridges. The ejector and positioner mechanisms of these types provided structure for engaging the rear portion of cartridges to enhance the positioning and extraction functions. These types of mechanisms provided structure for proper seating both rimmed and rimless cartridges in the rear of weapon cylinders, while also making the cartridges more easy to load.
Problems existed, however, with forward portions of the cartridges in weapons of this type. It was typical to provide stepped surfaces along the interior cylinder walls to allow proper acceptance and seating of the cartridges. With stepped cylinder walls, the cartridge casing material, which was typically of brass, would be forced against the step surfaces during use as the weapon was fired. If pressures were sufficiently high, the brass material could even flow to some extent. Thus, in certain instances the cartridge casing might tend to stick or resist extraction after firing. The cartridge could be removed relatively easily, but extraction and reloading times would be considerably slowed.
Portions of the cartridge case in some instances after use in stepped cylinders would enlarge. The enlargement could be to such an extent due to high pressure flow that the cartridge case became unsuitable for further reloading. In some additional cases with step surfaces in the cylinder walls, the cartridge case could shear or split or burst as a result of high pressure flow.